The present invention concerns a method as well apparatus for scanning and digitizing photographic images from photographic film.
In order to process individual images on photographic film, and then to print them on paper using, for example, a laser printer, the images must be scanned at high resolution and then digitized. One difficulty encountered during this process is the loss of information or resolution. This is normally caused by the fact that, for technical reasons, the smallest piece of information recordable on film is smaller than the resolution of the reading device. In other words, the number of data bits per square unit on the film is greater than that of the reading device. The grain size of a film is smaller than the pixel size of a digital reader device such as a suitable CCD array (for example, a CCD chip with 2042xc3x973072 pixels).
Another problem encountered with a scanning and digitizing system is that the format size can vary from film to film, so that the format of an individual image may not always agree with that of the CCD array. For example, images on a roll of film may have formats of either 60 mmxc3x9745 mm or 60 mmxc3x9790 mm. In such cases, not all pixels of the CCD array may be used to receive the image. This leads to a further reduction in scanning resolution.
The principal objective of the present invention is to improve upon a method and reading device of the type described above so as to realize improved resolution from a variety of film types and formats using such a reading device.
This objective, as well as other objectives which will become apparent from the discussion that follows, are achieved, according to the present invention, by providing a reader device having a photo-sensitive surface comprising a large number of pixels arrayed longitudinally and laterally, and by displacing the reader device rotationally and/or linearly by a distance of several pixels before and/or during the digitization process.
The present invention is thus able to take into account the various sizes (dimensions, landscape or portrait format, etc.) of differing film types, as well as the results of the asymmetry of a rectangular CCD chip, and take advantage of this. A particular advantage of the invention is the increase in image quality of large-format prints. For such prints, the disadvantages of existing technology set forth above with respect to resolution loss during digitization of negatives are particularly severe.
A further advantage of the invention is to be found in the expanded range of application with respect to film types and formats using the same reader device and obtaining optimum resolution.
Another advantage is that the reader device may be rotated or otherwise displaced in order to allow so-called xe2x80x9ceccentric croppingxe2x80x9d with optimum resolution for all negative formats.
A further advantage is that the reader device contains a sensitive surface with longitudinal and lateral axes. Movement of such an asymmetrical reader device, and especially its alignment before the reading or scanning process, can be especially advantageous for resolution optimization. The reader device preferably includes a CCD, particularly with a rectangular photo-sensitive area.
Using a preferred version of the invention, the reader device is aligned with the exposed areas before the reading process in order to adjust the optimum resolution.
In order to optimize the resolution, it is preferable to set the alignment of the reader device depending on the dimensions of the exposed area of a film.
It is preferable that the exposed areas have a longitudinal and a lateral dimension, and that the reader device be so aligned before reading that the longitudinal dimension of the photo-sensitive area is basically parallel to the longitudinal dimension of the exposed areas. In this manner, the existing asymmetries are used to optimize the resolution and to minimize information loss during scanning.
It is advantageous to align the reader device by rotating it, especially by rotating it in its plane by ninety degrees. This allows a CCD to so positioned that its orientation may be set to the orientation providing the best resolution.
It is also preferable that the reader device perform a number of reading passes over a specified, exposed area of a film (or of an image), and that the sampled values be compiled into an overall digital image. Individual image areas may be read in an overlapping or adjacent manner. An overlap, for example, may be especially helpful in order to compensate for regional differences in brightness of scanner illumination.
In order to compile different image areas using several reading passes, the reading device is displaced between subsequent reading passes, preferably linearly.
If an image is to be read twice, the reading device is displaced by about half of its width or length (or the width or length of the sensitive area) between reading passes. This displacement is performed within a plane.
It is advantageous that the reading device be displaced by about half of its width and length (or the width and length of the sensitive area), thus performing four individual reading procedures per image.